In manufacturing of semiconductor devices, various processing apparatuses (semiconductor-manufacturing apparatuses) are used to perform various processes, such as oxidizing, diffusing and CVD (Chemical Vapor Deposition), to process objects, such as semiconductor wafers (hereinafter, also referred to simply as “wafers”). As one type of such processing apparatuses, there has been known a batch-type heat treatment apparatus (e.g., a vertical heat treatment apparatus) that performs a heat treatment (thermal process) to a large number of wafers at a time (refer to JP2001-237238A, for example).
One example of the vertical heat treatment apparatus is a low-pressure diffusion apparatus, part of which is shown in FIG. 13. The low-pressure diffusion apparatus of FIG. 13 includes: a processing vessel 3 (process tube) made of quartz that accommodates wafers therein to perform a heat treatment to the wafers under reduced pressure; a metallic lid 15 that supports thereon a not shown holder (wafer boat) for holding a large number of wafers so as to load and unload the holder into and from the processing vessel 3 and to close and open the furnace throat 2a; and an O-ring 32 (annular sealing member) disposed on the peripheral portion of the lid 15 to seal a gap between the lid 15 and the furnace throat 2a of the processing vessel 3 (specifically, furnace throat flange 3a).
Another example of the vertical heat treatment apparatus is a low-pressure CVD apparatus, part of which is shown in FIG. 14. The low-pressure CVD apparatus of FIG. 14 includes: a processing vessel (not shown) made of quartz having a lower opening that accommodates wafers therein to perform a heat treatment to the wafers under reduced pressure; a metallic manifold (throat member) 50 connected to the lower portion of the processing vessel to provide a furnace throat 2a; a metallic lid 15 that supports thereon a not shown holder (wafer boat) for holding a large number of wafers so as to load and unload the holder into and from the processing vessel 3 and to close and open the furnace throat 2a; and an O-ring 32 disposed on the peripheral portion of the lid 15 to seal a gap between the lid 15 and the manifold 50.
In the former heat treatment apparatus shown in FIG. 13, when the internal pressure of the processing vessel 3 is reduced, the O-ring 32 between the lid 15 and the furnace throat 2a (more specifically, the throat flange 3a) is squashed so that direct contact between the lid 15 and the throat 2a occurs. Due to this, contact pressure is exerted on the furnace throat 2a, resulting in damage of the furnace throat 2a such as cracking, and generation of particles due to micro cracks.
In the latter heat treatment apparatus shown in FIG. 14, when the internal pressure of the processing vessel 3 is reduced, the O-ring 32 between the lid 15 and the manifold 50 is also squashed so that direct contact between the lid 15 and the manifold 50 occurs. This causes chafing between the lid 15 and the manifold 50 due to difference in their thermal expansions, resulting in metallic contamination of wafers.